Why do you keep trying to peddle Spectrums junk modems. Maybe I don't want a tech at my house every 2 weeks, or maybe I don't want their throttled modem. Feel free to take their "free" modem, and just remember, you get what you pay for.
Not sure what you mean by either of the phrases "Spectrum's junk modems" or "their throttled modem." You choose to subscribe to one of their internet service tiers that you decided is useable for your purpose and reasonably priced. In return they provide you with a modem good for that tier's top speed, at no monthly charge. Nobody twisted your arm. If you don't want to use their free modem, fine.
Purchase your preferred modem from your favorite consumer electronics store and pay to fix it whenever it hiccups or needs a code update. But don't try to turn their loaner unit concept into 'speed throttling', which has a rather strict FCC definition and is (sadly) no longer prohibited by the FCC.
A customer should have the right to purchase any modem they deem fit. Cable modem manufacturers require cable companies to push the updates, and it is something that is not user upgradable. There is no reason that when a code update is needed that spectrum could not push the update. Mobile phone companies do not force you to use specific phones; rather they give you a SIM card and allow you to put your device on the network. Some people don’t have offices that are within a 10 minute distance and don’t want to drive 30 minutes or longer. If the consumer feels that they don’t want cable company equipment in their house, which the fcc permits.
As a Spectrum customer you have the right to use your own modem for data, so long as Spectrum has determined that the modem will not adversely impact its network or your neighbors. Whether or not a firmware update is needed and won't adversely impact the network isn't something an ISP is going to leave up to Netgear or Arris engineers. They will do their own testing and if they determine the update is needed and won't cause problems they will push out the updates...and not a second before.
Who do you think a customer would blame if ISPs allowed the modem manufacturers to push updates directly and one happened to cause massive slowdowns?